Patent GB-465926-A (GB)
Title: A variable speed gear box particularly for automobiles
IPC: F16H61/02
Filed: 1936-06-11
Abstract: 465,926. Fluid-pressure servomotorcontrol systems. COPPA, M. June 11, 1936, No. 16342. [Class 135] [Also in Groups XXIV, XXVIII, and XXXIV] Change-speed epicyclic gearing is controlled by a single lever 73, which is turned in its own plane to rotate a profile selector-bar 44 mechanically and moved in a plane at rightangles to energize a double-acting follow-up hydraulic servomotor 50 which thrusts the profile-bar axially in either direction for neutralizing or engaging a selected speed. At the end of a gear-engaging stroke, the selected speed is positively locked in, and the hydraulic pressure is cut-off by disabling the oil-pump. In operation the hand-lever 73 is first lifted vertically (position a) to energize the servomotor 50 for movement of the profile-bar 44 to the right of Fig. 3, thereby neutralizing the gear ; is then turned selectively to rotate the profile-bar through a sleeve 74 and Bowden or other mechanism 48; and is finally depressed vertically (position b) to energize the servomotor for leftward movement of the profile-bar for establishing the selected speed. The profile-bar 44 carries selectively-arranged wedges 1st, 2nd &c., the inclined sides of which, as the bar is moved from right to left of Fig. 3, lift a selected rollerfollower 37, Fig. 2, which remains positively locked in a recess on the upper surface of the wedge without the further application of hydraulic power. The roller-followers 37 operate brakes and a direct-drive clutch, as described below. The profile-bar 44 is rotatably connected at 49 to the piston-rod of the servomotor 50. The servomotor 50 is energized in either direction by the vertical movements of the lever 73, acting through a rod 76, Bowden or other mechanism 61, and a rotatable sector 54, having a helical slot engaging a pin 55 on a slide 56 so as to impart axial movement to the slide. The slide 56 carries a pinion engaging a pair of racks, one 57 being connected for axial movement at 58 with the profile-bar 44, the other 53 being connected to a balanced doublevalve 51, governing pressure-inlet or exhaust of oil from both sides of the servomotor 50. The arrangement constitutes a follow-up device, since the movement of the profile-bar 44 acts through the rack 57 to reverse the movement of the valve 51 and stop the bar in any intermediate position corresponding to that of the lever 73. Such position, allowing slip in the change-speed gear is maintained by virtue of overlap in the valve 51, whereby, when the valve reaches a certain stage in its reversed movement exhaust ports g or a on the idle side of the valve communicate with adjacent pressure-inlet ports f or b, before the pressureinlet c or e to the operative side of the piston is closed, so that the pressure oil leaks to an amount determined by that necessary to support the load, and the piston is stopped dead. When the gear is fully engaged an additional helical slot on the sector 54 acts to put out of action the hydraulic pump 87, Fig. 6, which is continuously driven by an engine camshaft A. This disablement of the pump is effected by a rack 102, operated by the sector 54, and serving to retract a sleeve-abutment 98 of a spring 97, which normally presses a roller-tappet 95, carried by the pump-plunger 87, against the camshaft A. The plunger is thereby relieved of its cam-following pressure and ceases to reciprocate. The selector profile-bar 44 is prevented from rotation, except in neutral, by a fixed stud 64, Fig. 2, engaging grooves 65 in the bar. The clutch and brakes of the epicyclic gear are operated through springs 38 by rods 30, Fig. 2, carrying rollers 37 which co-operate with the raised wedges on the profile-bar 44 in the manner above-described. Emergency manual operation is provided for by an external linkage directly screwing in the servo piston 50 after removal of plugs 62, 63, 66, and the pin 60.